1. Field of the Invention
This invention relates generally to watermattresses and their methods of construction and more specifically to that type of watermattress forming a single fluid cavity and having corner reinforcement means.
2. Prior Art Statement
As watermattresses have increased in popularity, it has become particularly desirable to devise mattresses and methods which can facilitate mass production. One step that has been taken in this effort has been to form a water bladder from substantially a single piece of material. In many of these constructions, a single piece of substantially rectangular material has been folded back on itself to form the two major surfaces of the mattress. Joining the ends of the rectangular piece has produced a desirable tubular construction. Marginal portions at the ends of the tube have been overlapped and sealed to substantially enclose the bladder with only the corners remaining to be sealed.
Unfortunately, it is the seals at the corners of such a construction which have been particularly critical. At the corners one is not dealing with merely two overlapping sheets as in most lap seam constructions. Rather, one is concerned with sealing two regions wherein three substantially perpendicular planes intersect.
In some constructions it has been found desirable to provide an insert at each of the corners in order to reinforce those regions of the mattress. Such is the case with the mattress disclosed by Kuss in U.S. Pat. No. 3,753,823. Unfortunately, the method taught by Kuss results in an exceedingly large seal at each of the corners of the mattress. Instead of reinforcing the corners, this seal appears to be smashed and tends to weaken the corners resulting in a mattress of reduced integrity.
Phillips discloses another mattress of this general type in U.S. Pat. No. 4,025,975. This mattress is also provided with a corner insert, but in this case, the insert has a rather complex seal pattern. In fact, seals must be made in four different planes of the insert; this significantly increases the complexity of construction. The method of manufacturing this mattress is further complicated by the fact that the seals associated with the insert must be made with more than one heat sealing step at each of the corners of the mattress.
Other watermattress disclosures of which the applicant is aware include the following U.S. Pat. Nos. 3,778,852, 3,842,455, 3,918,110, 4,015,299, 4,055,867.
These disclosures are not believed to be as pertinent to the instant invention as those discussed in greater detail above.
Even with these constructions of the prior art, it has remained desirable to provide a mattress which can be mass produced with a minimum of material handling and a minimum of heat sealing steps. A mattress with increased integrity is also desirable and this is typically associated with a reduced area of heat weld. The provision of a corner insert to reinforce this area of significant stress has also remained desirable.